1. Field of the Invention
The invention generally relates to position detection apparatus for use in measuring and gaging systems. More particularly, the invention concerns mechanical repositioning apparatus for use with a contact detection probe.
2. Description of the Prior Art
Automated machining systems and coordinate measuring systems require a precise means of locating surfaces of work parts. One method of such measurement, to which this invention pertains, utilizes detection of mechanical contact by a reference probe with the surface being measured in conjunction with a determination of the x, y and z axes location of the table or machine spindle at the time of reference probe contact. The accuracy of this approach depends on the capability of the detection system for accurately returning the probe to a predetermined rest position whenever no external contact force is being exerted on the probe. Further, since such contact force could displace the probe in any direction, the return or repositioning apparatus must be operative to accurately and repeatably restore the rest position state regardless of the direction of the prior probe displacement caused by contact with the surface undergoing measurement.
One prior art approach attempting to achieve a repeatably attainable probe rest position is disclosed in U.S. Pat. No. 4,270,275 - McMurtry, U.S. Pat. No. 4,153,998 - McMurtry, and U.S. Pat. No. 4,279,080 - Nakaya, each generally teaching a probe rest position defined by a plurality of locations or nests comprised of a pair of converging surfaces on either the moveable probe or a fixed reference point of the probe housing, said converging surfaces engaged by a curved surface on the other of either the moveable probe or fixed reference point.
Another prior art approach attempting to meet the same general objective of accurate probe repositioning uses a complex interconnection of reed springs. Such approaches are taught, for example, in U.S. Pat. No. 3,869,799 - Near et al., U.S. Pat. No. 4,084,323 - McMurtry, and U.S. Pat. No. 4,158,919 - McMurtry.
Notwithstanding the prior art approaches, there continues to be a long-felt need in the automated measuring art for a structurally simple, rugged, economic and repeatably accurate touch probe mechanical positioning system which is compatible with a variety of electrical or electro-optical contact detection indicating signal generator circuitry.